generic/299: make sure fio really exits

Fix two problems in generic/299

1. Remove $seqres.full before test, otherwise the file is growing all
the time.

2. Make sure fio really exits, otherwise fio would block umount. $pid is
the pid of function run_check not fio, sometimes fio is still there when
$pid is dead and blocking umount.

Signed-off-by: Eryu Guan <eguan@redhat.com>
Reviewed-by: Theodore Ts'o <tytso@mit.edu>
Signed-off-by: Dave Chinner <david@fromorbit.com>

tests/generic/299

@@ -109,6 +109,8 @@ rw=randrw
 filename=buffered-aio-verifier
 EOF
 
+rm -f $seqres.full
+
 _require_fio $fio_config
 _require_xfs_io_command "falloc"
 
@@ -136,7 +138,7 @@ _workout()
 	    done
 	    # Following like will check that pid is still run.
 	    # Once fio exit we can stop fallocate/truncate loop
-	    kill -0 $pid > /dev/null 2>&1 || break
+	    pgrep -f "$FIO_PROG" > /dev/null 2>&1 || break
 	done
 	wait $pid
 }